Process of preparing direct-acidified milk beverage keeping high viable cell count at ambient temperature

ABSTRACT

The invention provides a process of preparing direct-acidified milk beverage keeping high viable cell count at ambient temperature. The process means that, adopting conventional technology to prepare acidified milk beverage and sterilizing, then adding  Lactobacillus rhamnosus  ATCC 53103 and certain quantity of growth promoting factors under aseptic condition. According to various pH value, the product can be stored at ambient temperature for 1-6 months and the viable cell count will not be less than 10 5  cfu/ml milk beverage. The indexes of storage period and viable cell count are much higher than fermented milk beverage prepared by conventional process. Thereby it overcomes the defects that direct-acidified milk beverage with long shelf life has no viable lactic acid bacteria and has low nutritional value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of international application No. PCT/CN2007/002035 filed on Jun. 29, 2007, which claims the priority benefits of China application No. 200710064896.X filed on Mar. 28, 2007. The contents of these prior applications are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to milk beverage field, in particular, a process of preparing direct-acidified milk beverage keeping high viable cell count at ambient temperature.

TECHNICAL BACKGROUND

Direct-acidified milk beverage is highly appreciated by consumers especially children and women because of its smooth, sweet and sour taste. Using milk as base, acidulants, sweeters, flavourings, thickening and emulsifying stabilizers are added and mixed together to obtain acidified milk beverage containing more than 1.0% protein, and after being sterilized, its shelf life can reach to 3-6 months. Since such products are not fermented by lactic acid bacteria, the nutrition value is not high.

It is desirable for the manufactory of acidified milk beverage that viable lactobacillus can be added into direct-acidified milk beverage and kept viable for long time without negative influence to its taste. However, up to now, no relevant technology has been reported. Usually when lactobacillus is added into milk, they will metabolize lactose to produce lactic acid, thereby make the mouthfeel of product unacceptable to consumers. Meanwhile, the activity of lactobacillus is decreased gradually; by the end viable cell count can not be measured. And ambient temperature environment will speed up the process greatly.

Some documents have reported processes for increasing the viable cell count of lactobacillus. These processes include: adding antioxidant (such as VC), adding prebiotics(such as oligosaccharides), encapsulating lactobacillus into microcapsule, non-adding Lactobacillus bulgaricus and decreasing oxidation-reduction potential (such as adding cysteine) etc . . . (NP. Shah, Probiotic bacteria: Selective enumeration and survival in dairy foods, J. Dairy Sci., 83:894-907, 2000; A. Lourensand B. C. Vijoen Int. Dairy J., 11: 1-17, 2001). However, the effect of these processes is very limited.

Lactobacillus rhamnosus (available from American Type Culture Collection, bacterial strain number: ATCC 53103 ) is a probiotic strain isolated from healthy human body (U.S. Pat. No. 4,839,281; U.S. Pat. No. 5,032,399), and it can get rid of endotoxin from blood plasma (U.S. Pat. No. 5,413,785). The distinctive character of this bacterium is that it does not metabolize lactose and is resistant to acid and oxygen. Since this bacterium has the function of prevention and treatment of stomach upset (such as diarrhea) and improvement of immunity, it is used in healthy and functional products (such as yoghourt). The details of the biological characteristics and probiotic function of this bacterium please refer to above-mentioned patents and review article M. Saxelin, Lactobacillus GG A human probiotic strain with thorough clinical documentation, Food Rev. Int., 13 :293-313, 1997.

SUMMARY OF INVENTION Technical Problem to Be Solved

One aspect of the invention is to provide a process of preparing direct-acidified milk beverage keeping high viable cell count at ambient temperature.

Technical Solutions

The process according to an embodiment of the invention includes: according to the characters of Lactobacillus rhamnosus ATCC 53103 that it can not metabolize lactose to produce lactic acid and can survive for a long time, adding this bacterium into direct-acidified milk beverage under aseptic conditions, meanwhile adding 0.01-5% wt of growth promoting factors, thereby obtaining direct-acidified milk beverage keeping high viable cell count at ambient temperature during storage.

The term “ambient temperature” herein refers to a temperature which can be reached indoor under normal conditions, such as 0-40° C., preferably 10-30° C.

In the process according to an embodiment of the invention, milk is directly acidified to pH value 4.0-4.5 without fermentation, so as to obtain acidified milk beverage. Then sterilize and add concentrated culture, concentrated frozen culture or freeze dried culture of Lactobacillus rhamnosus ATCC 53103 together with 0.01-3% wt of growth promoting factors under aseptic condition.

Wherein, said milk beverage is made from fresh milk or reconstituted milk (including but not limited to fresh milk or reconstituted milk of cow milk or goat milk). The protein concentration of the milk beverage is 0.1-4%. Preferably, the protein concentration of the milk beverage is 0.7-2.5%.

In the process according to an embodiment of the invention, the acidulants for adjusting pH value can be any acidulants which are known by people skilled in the art, such as one or more of citric acid, lactic acid and malic acid.

The pH value of finished product of direct-acidified milk beverage is 3.5-4.8, preferably 3.7-4.4.

In the process according to an embodiment of the invention, the addition amount of Lactobacillus rhamnosus ATCC 53103 is not limited theoretically. According to the principle of economy and effectiveness, the addition amount of Lactobacillus rhamnosus ATCC 53103 is 10³-10⁸cfu/ml milk beverage, preferably 10⁴-10⁷ cfu/ml milk beverage.

In the process according to an embodiment of the invention, above-mentioned growth promoting factors can be any growth promoting ingredients known by people skilled in the art that can be utilized by Lactobacillus rhamnosus except lactose. Preferably, said growth promoting factors can be selected from one or more of glucose, fructose, galactose, arabinose, ribose, mannose, rhamnose, fucose, tagatose, sucrose, maltose, cellobiose, trehalose, melizitose, gentiobiose, galactitol, mannitol, sorbitol, inositol, gluconic acid, salicin, aescine, arbutin, amygdalin and acetylglucosamine, and the addition amount is 0.01-5% wt. It can be added together with milk base before sterilization or with Lactobacillus rhamnosus ATCC 53103 after sterilization under aseptic condition.

More preferably, the growth promoting factors are selected from one or more of glucose, fructose, galactose and sucrose, the addition amount is 0.05-3% wt.

Sweeters, flavorings, stabilizers and preservatives can also be added into the above-mentioned direct-acidfied milk beverage.

Wherein, sweeters can be selected from one or more of aspartame, Acesulfame-K (Ace-K), Sodium cyclamate, stevia sugar (stevioside) and Trichlorosucrose. And the addition amount can be 0.001-5 g/L, preferably 0.1-1 g/L.

Flavourings can be selected as seasoners, and the addition amount can be 0.001-5 g/L, preferably 0.1-1 g/L.

Stabilizers are selected from one or more of pectin, gelatin, modified starch, glyceryl monostearate, sucrose esters and sodium carboxymethyl Cellulose, and the addition amount can be 0.001-12 g/L, preferably 0.1-10 g/L.

Preservatives are selected from one or more of natamycin and potassium sorbate. And the addition amount is 0.001-3 g/L, preferably 0.005-0.5 g/L.

ADVANTAGEOUS EFFECTS

The direct-acidified milk beverage prepared by the process according to an embodiment of the invention can be stored for 1-6 months under room temperature (10-30° C.) and keep viable cell count at least 105 cfu/ml milk beverage. The indexes of storage period and viable cell count are much higher than fermented milk beverage prepared by conventional process. Thereby the defects that directed-acidified milk beverage has no viable Lactobacillus and has low nutritional value are overcome.

DESCRIPTION OF EMBODIMENTS

The following examples are used to illustrate the invention, but not to limit the scope of the invention.

EXAMPLE 1 Direct-Acidified Milk Beverage Prepared with Lactobacillus rhamnosus and its Storage Test

Add 3.5% whole milk powder into fresh milk containing 11.5% milk solid; thereby obtain whole milk with 15% milk solid. Use 700 ml of water at 70° C. to resolve acidic milk beverage stabilizer SY-601 (provide by BEIING FUMENGTE BIOTECHNOLOGY COMPANY LTD.) 6 g and Ace-K ( available from ZHANGJIAGUANG HAOBO CHEMISTRY COMPANY) 5 g, stir for 20 minutes and cool down to below 25° C. After hydration for 30 minutes, add 200 ml above mentioned reconstituted whole milk into 700 ml stabilizer solution and stir for 5 minutes. Adjust the pH value of the mixture to 4.5 with 10% citric acid, adjust the volume to 1000 ml with water, continue to stir for 5 minutes. Preheat to 70° C., then homogenize with pressure 20 MPa, then sterilize at 115° C. for 15 minutes. The above procedure is the conventional method to prepare direct acidified milk beverage which is known to people skilled in this field.

Cool it down to below 37° C., inoculate this acidified milk beverage with Lactobacillus rhamnosus ATCC 53103 ( concentrated culture) with quantity of 1.5×10⁶ cfu/ml and 0.02% glucose aseptically. Keep the milk beverage at 37° C. for 15 days then 28° C. for 45 days, measure its pH value, acidity and viable cell count. The results are listed in table 1.

TABLE 1 Viability of lactobacillus and the pH value & acidity variation of the acidified milk beverage during storage Viable cell Storage storage time Titratable count (×10⁶/ml temperature (day) pH value acidity milk beverage) 37° C. 0 4.50 35 1.5 1 4.44 33 22 3 4.47 35 16.7 6 4.50 35 14.2 9 4.53 31 3 12 4.53 31 3.6 15 4.54 30 3.6 28° C. 18 4.57 28 2.5 24 4.52 32 1.2 27 4.57 28 1.6 30 4.56 31 0.9 37 4.56 31 1.1 60 4.59 29 0.68

EXAMPLE 2 Direct-Acidified Milk Beverage Prepared with Lactobacillus rhamnosus and its Storage Test

Prepare reconstituted whole milk with 10% whole milk powder and make a mixture with 1.0% milk protein by the same process as in Example 1, adjust the pH value of the mixture to 4.2 with 10% lactic acid. Adding 0.1% glucose, 0.4% sucrose inside the mixture, homogenize and sterilize, then cool it down to below 37° C., add Lactobacillus rhamnosus ATCC 53103 (concentrated frozen culture) with quantity of 1.5×10⁵ cfu/ml into above-mentioned acidified milk beverage, store it at 12-25° C. Measure the pH value and viable cell count in different storage period. The results are listed in table 2.

TABLE 2 Viability of lactobacillus and pH value variation of the acidified milk beverage during storage Viable cell count storage (10⁶ cfu/ml time (month) pH value milk beverage) 0 4.2 2 1 3.8 98 2 3.82 34 3 3.80 7.6 4 3.85 2.1 5 3.85 0.9 6 3.83 0.25

EXAMPLE 3 Direct-Acidified Milk Beverage Prepared with Lactobacillus rhamnosus and its Storage Test

With the same process in Example 1, make reconstituted whole milk with 4.5% whole milk powder, and acidify it. Adjust the pH value of the mixture to 4.0 with 10% lactic acid. Homogenize and sterilize, then cool it down to below 37° C., add Lactobacillus rhamnosus ATCC 53103 (freeze dried culture powder) with quantity of 2×10⁶ cfu/ml and 0.15% galactose into above-mentioned milk beverage aseptically, store it at 12-25° C. Measure its acidity and viable cell count during storage. The results are listed in table 3

TABLE 3 Viability of lactobacillus and pH value variation of the acidified milk beverage during storage Viable cell count storage (10⁶ cfu/ml time (month) pH value milk beverage) 0 4.2 0.15 1 4.1 210 2 4.09 180 3 4.11 110 4 4.08 82 5 4.07 32 6 4.08 8.5

EXAMPLE 4 Direct-Acidified Milk Beverage Prepared with Lactobacillus rhamnosus and its Storage Test

With the same process in Example 1, make reconstituted whole milk with 7% whole milk powder, and acidify it. Adjust the pH value of the mixture to 4.4 with 10% malic acid. Homogenize and sterilize, then cool it down to below 37° C., add Lactobacillus rhamnosus ATCC 53103 ( concentrated frozen culture) with quantity of 2×10⁷ cfu/ml and 0.02% fructose into above-mentioned milk beverage aseptically, store it at 12-25° C. Measure the pH value and viable cell count during storage. The results are listed in table 4.

TABLE 4 Viability of lactobacillus and pH value variation of the acidified milk beverage during storage Viable cell count storage (10⁶ cfu/ml time (month) pH value milk beverage) 0 4.40 20 1 4.30 245 2 4.31 178 3 4.30 105 4 4.28 92 5 4.35 65 6 4.29 48 

1. A process of preparing direct-acidified milk beverage keeping high viable cell count at ambient temperature, wherein milk beverage is not through fermentation, directly by adjusting pH value to 4.0-4.5 to obtain acidified milk beverage, then sterilizing, adding concentrated culture, concentrated frozen culture or freeze dried culture of Lactobacillus rhamnosus ATCC 53103 together with 0.01-3% wt of growth promoting factors under aseptic condition.
 2. The process according to claim 1, wherein said milk beverage is made from fresh milk or reconstituted milk, the protein concentration of the milk beverage is 0.1-4%;
 3. The process according to claim 2, wherein the protein concentration of the milk beverage is 0.7-2.5%.
 4. The process according to claim 1, wherein the acidulants for adjusting pH value are selected from one or more of citric acid, lactic acid and malic acid.
 5. The process according to claim 1, wherein the pH value of the finished product of acidified milk beverage is 3.5-4.8.
 6. The process according to claim 5, wherein the pH value of the finished product of acidified milk beverage is 3.7-4.4.
 7. The process according to claim 1, wherein said addition amount of Lactobacillus rhamnosus ATCC 53103 is 10³-10⁸ cfu/ml milk beverage.
 8. The process according to claim 7, wherein said addition amount of Lactobacillus rhamnosus ATCC 53103 is 10⁴-10⁷ cfu/ml milk beverage.
 9. The process according to claim 1, wherein said growth promoting factors are selected from one or more of glucose, fructose, galactose, arabinose, ribose, mannose, rhamnose, fucose, tagatose, sucrose, maltose, cellobiose, trehalose, melizitose, gentiobiose, galactitol, mannitol, sorbitol, inositol, gluconic acid, salicin, aescine, arbutin, amygdalin and acetylglucosamine, the addition amount is 0.01-5%, and it can be added together with milk base before sterilization or with Lactobacillus rhamnosus ATCC 53103 under aseptic condition.
 10. The process according to claim 9, wherein said growth promoting factor is selected from one or more of glucose, fructose, galactose, sucrose, and the addition amount is 0.05-3%.
 11. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 1. 12. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 2. 13. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 3. 14. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 4. 15. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 5. 16. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 6. 17. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 7. 18. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 8. 19. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 9. 20. A direct-acidified milk beverage keeping high viable cell count at ambient temperature prepared by the process according to claim
 10. 